Are mortal sins much rarer than we thought?

I don't mean, do we commit acts that are objectively and gravely wrong less often than we thought? I mean: how rare is it that, in committing an objectively wrong act involving grave matter, we act with full knowledge and full consent of the will?--keeping in mind that, according to Catholic teaching, an action needs to involve all three elements to be a mortal sin.

Just how prevalent are genuine mortal sins?

Well, it's kind of a trick question. We'll never know the answer--not about other people, not even about ourselves. No CBS commentator will ever announce, "Mortal sins rose by 3.2% this quarter, though experts differ on how much of the increase is due to a simultaneous drop in invincible ignorance." God keeps that knowledge to Himself, and for good reason. Could anybody imagine we'd put it to good use if He let us in on it?

And as Kate Cousino asked plaintively when I broached the subject on Facebook the other day:

Is it overly simplistic to say we do the best we can, walking in faith, and trust God to sort out the culpability in His perfect justice and mercy?

If mortal sin involves not only grave matter, but also full knowledge and full consent of the will, is it very likely that – given the agonizing complexity of most cases of irregular marriage – such “full knowledge” and “full consent” are very possible? Note that I am not questioning the absolute objectivity of right and wrong. I am, however, questioning the degree to which subjective culpability can ever be absolute.

I wonder, though, if we need to unpack more fully what we mean by "full knowledge" and "full consent." Rebecca seems to set the bar pretty high--or at least, her estimation of people's abilities pretty low:

Given how stupid we all are, full knowledge even of the simplest truths must be very rare indeed. And given what we know about neuroscience, full consent of the will is not really possible for most of us, most of the time. This is a humbling thought.

I'm not sure what neuroscience she's referring to, but she has a point: our knowledge is very limited, and sin makes us stupider still. We tend to believe what we want to believe, and of the reality we do manage to discern, we pick and choose the bits that fit best with the fixed ideas that already populate our heads. It's possible to integrate new knowledge into our mindset, and it's possible to experience a metanoia and set about trying to live in light of the truth, but it takes work, and it takes grace. It's not the norm.

I'm not saying we're altogether incapable of knowledge or free consent of the will (and nor does Rebecca). Theories that deny free will have to ignore our immediate experience of exercising it. You don't need to take it on faith; you don't need to be an expert in moral theology or anthropology or neuroscience. Your immediate experience of your own acts confirms it.

But full consent of the will...maybe that's a different matter.

It's true that sometimes we think we're acting freely and realize upon reflection that we were acting under pressure to please someone, or to avoid offending someone else--or that we were being manipulated to choose something we only thought we wanted.

Then, too, our freedom is deeply compromised by concupiscence and malice. As St. Paul complains in his letter to the Romans, "I do not understand my own actions. For I do not do what I want, but I do the very thing I hate." We all know what he's talking about.

So our knowledge is limited--but it's real knowledge. Our free will is compromised--but not overthrown altogether. I guess the question is: What does "full knowledge" and "full consent of the will" mean? Are they really all that rare? If we knew the answer to that, we still wouldn't be able to see into everybody's souls, or even our own. But maybe we'd have a clearer idea of when mortal sin is occurring and when it isn't.